Features of waffle raft slabs
The features of waffle raft slabs include the following:
- they are used on flat sites
- they are wholly above ground
- no beam excavation is required
- no controlled or rolled fill is used
- cardboard slab panel/void formers are used
- slab panels are on 1 metre grids (approximately)
- trench mesh or individual bars can be used
- slab thickness is 85 mm
- internal beams are 110 mm wide
- there is minimal concrete volume
- no beam down drag from clay (above ground slab) occurs
- shrinkage of slab is lower than stiffened rafts and footing slabs
- they use 30% less concrete than a stiffened raft
- they use 20% less steel than a stiffened raft.
This construction is rarely used on Class A and Class S sites.